Variable displacement hydraulic pump

ABSTRACT

A variable-capacity, positive displacement pump having a rotor, pumping vanes or slippers carried by said rotor, a cam ring surrounding said rotor and cooperation therewith to define pumping chambers, a pump body surrounding said cam ring and connected thereto with a pivotal connection whereby the pump body and the cam ring define opposed pressure chambers, and regulator valve means for controlling the pressures distributed to each of said pressure chambers whereby the position of said ring with respect to said rotor may be changed to vary the displacement of the pump.

iinited Mates Patent a Leonard 51 A r. W W72 [54] VARIABLE DISPLACEMENT2,985,109 5/1961 Ernst ..4l8/26 HYDRAULIC PUMP 5 252 221 24:22; r at----::;s

' e ance eta [72] Inventor: Allan S. Leonard, Westland, Mich. y

- Primary Examiner-William L. Freeh [73] Asslgnee' Ford, Motor CompanyDearbom Mlch' Attorney-John R. Faulkner and Donald J. Harrington [22]Filed: Apr. 2, 1970 211 App]. No.: 24,985 [57] ABsTmCT Avariable-capacity, positive displacement pump having a rotor, pumpingvanes or slippers carried by said rotor, a cam ring g g surrounding saidrotor and cooperation therewith to define I pumping chambers, a pumpbody surrounding said cam ring [5 8] Field of Search ..417/220, 218,418/26, 30 and connected thereto with a pivotal connection whereby thepump body and the cam ring define opposed pressure chaml56] Referencescued bers, and regulator valve means for controlling the pressuresUNITED STATES PATENTS distributed to each of said pressure chamberswhereby the position of said ring with respect to said rotor may bechanged .-4l to vary the displacement of the pump 2,724,339 11/1955OConnor et al. .....4l8/26 2,81 1,926 1 H1957 Robinson, Jr ..4l8/26 8Claims, 4! Drawing Figures n a/ms Prawn:

PATENTEBAPR 18 1912 SHEET 10F d II III allllll II lll lwlll 3 NW;

PATENTEBAFR 181972 3, 656,869

' SHEET 3 OF 4 flM/W 51 fowmeo VARIABLE DISPLACEMENT 1- My inventionrelates generally to positive displacement pumps, and is adaptedespecially to be used as a pressure source for control systems forautomatic power transmission mechanisms, although it is capable also ofother uses. One of the other uses may be a power steering pump in apower steering system for automotive vehicles. In the particularembodiment disclosed in this specification, provision is made foradapting the pump for use as an automatic power transmission pump whichwould be driven by the vehicle engine.

Automatic power transmission mechanismsrequire fluid pressure operatedservos, which control the relative motion of planetary gear elementsduring speed ratio changes. The servos are supplied with pressure from afluid pressure source, and a valve controlled circuit provides selectivepressure dis- .tribution from the pressure source to the servos as ratiochanges are accomplished.

The circuit pressure maintained in the servos should be adequate to meetchanging torque requirements. A high circuit pressure is required whenthe torque transfer through the driveline is high, but it should belowered when torque requirements are lower. The pump that suppliescircuit pressure to the system should be of sufficient capacity tosupply the most extreme pressure requirements. When the vehicle isoperating under conditions that do not require maximum torque delivery,the pump is required to bypass its fluid through a pressure regulatorvalve system since the pump output normally is maintained at a constantvalue for any given speed regardless of the torque being delivered.

My improved pump structure will make it possible to vary the capacity ofthe pump so that its fluid delivery is adequate to meet the existingtorque requirements for any given set of operating conditions, and neednot be designed for operation at maximum fluid delivery when high fluidflow is not required to maintain adequate circuit pressure. I haveachieved this variable capacity feature without the necessity for anincrease in the size of the pump beyond that size that would be requiredfor a conventional, fixed-displacement pump in a similar operatingenvironment. The invention may be adapted readily to existing fluidcircuits for automatic transmissions without the need for modifying thecircuitry or adding additional circuit elements.

The variable displacement characteristic is achieved by providing a camring that surrounds a pump rotor and by pivotally mounting the cam ringon the associated pump housing so that the eccentricity of the cam ringwith respect to the rotor may be changed when changes in fluiddisplacement are desired. The adjustable cam cooperates with thesurrounding housing to define separate pressure zones on its opposedsides. The zones are separated by sealing elements situated between theperiphery of the cam ring and the surrounding housing whereby the camring is subjected to opposed and balanced pressure forces. Fluidcircuitry including an automatic pressure regulator valve is in fluidcommunication with each of the pressure zones so that the pressurebalance or ratio of pressures across cam ring may be controlled.

The regulator valve circuitry includes a valve element having a pressurearea that is in fluid communication with one pressure zone on one sideof the cam ring. That same regulator valve element causes communicationbetween the other pres sure zone and a low pressure part of the system.This low pressure part of the system may be in fluid communication witha hydrokinetic torque converter in the automotive vehicle driveline, orit may be in fluid communication with an exhaust region. In any case,the regulating characteristics of the regulator valve element controlthe ratio of pressure forces acting on the cam ring. A change in thatratio can be induced by applying a regulating pressure force on theregulator valve element. That regulating force is made proportional to apressure signal that is related functionally to engine torque. Theoutput pressure established by the pump structure then is relatedfunctionally to the same signal. Any excess pump displacement beyondthat required to maintain the necessary circuit pressure will bebypassed to the converter or to the exhaust region, as appropriate.

BRIEF DESCRIPTION OF THE FIGURE OF THE DRAWING FIG. ll shows atransverse cross-sectional view of a positive displacement pump ofvariable capacity which includes the improvements of my invention. It istaken along the plane of section line 1-1 of FIG. 2.

FIG. 2 is a longitudinal cross-sectional view taken along the plane ofsection line 2-2 of FIG. 1.

FIG. 3 shows an alternate pivotal connection between the cam ring andthe pump housing which may be used instead of the pivotal connectionshown in FIG. ll.

FIG. 4 is a cross-sectional view similar to the cross-sectional view ofFIG. 1, although it shows a different pressure regulating valvearrangement in combination with positive displace ment pumping elements.

BRIEF DESCRIPTION OF THE INVENTION In FIG. ll, numeral 10 designates astationary pump housing. It includes a circular wall 12, which may bebolted to a shoulder formed in a power transmission housing for anautomotive vehicle driveline. The wall includes a circular opening 14which receives a bushing 16 in which is journaled sleeve shaft 18. Thissleeve shaft is connected to the impeller of a hydrokinetic torqueconverter, which in turn is driven by the vehicle engine not shown.

Pump housing It) includes a circular main bore 20. A circular cam ring22 is positioned within the bore 20, the diameter of the ring 22 beingless than the diameter of the bore 20. The

I open end of the bore 20 is closed by cover flange 24 secured tostationary support shaft 26. Flange 24 in turn is secured by bolts tothe wall 12.

Cam ring 22 is provided with a pivot extension 28 which is received in aregistering slot 30 formed in the wall of the bore 20. A sealing pin issituated in a sealing groove 32 formed in the outer periphery of the camring 22 at a location displace 180 from the extension 28. The sealingpin is identified by reference character 34. The location of the sealingpin 34 need not be directly opposite the extension 28. Its preciselocation is chosen to meet the special pressure balancingcharacteristics required by a particular design.

Rotatably mounted within the ring 22 is a rotor 36 which is providedwith a plurality of peripheral notches 38. A slipper element 40 ismounted loosely within each notch 38, and it is biased radiallyoutwardly by a slipper spring 42. The outer surface of the slipperengages the inner surface of the ring 22. The precise curvature of theslipper 40 at the slipper-cam ring interface is chosen so that a wedgeof lubricating oil will be developed between the slipper and the camring thus providing a fluid bearing seal.

A low pressure port of arcuate shape is provided in the housing asindicated by reference character 44. It communicates with a passage 46which in turn is in fluid communication with the transmission sump. Afluid pressure outlet port of arcuate shape is provided also in thehousing It) as indicated at 48. It is in fluid communication with thehigh pressure outlet passage 50, which communicates with a so-calledline pressure passage 52 which supplies circuit pressure for theautomatic transmission control circuit.

A rotor 36 is eccentrically positioned within the ring 22. It cooperateswith the cam ring to define a pumping cavity 54 of crescent shape. Therotor is arranged in general tangential disposition with respect to theinner surface of the cam ring 22, the point of tangency being generallyidentified by reference character 56.

The space between two adjacent slippers receives oil distributed to itthrough the port 44. This oil is carried through the crescent shapedpumping chamber and is delivered to the outlet port as the rotor rotatesin a counter-clockwise direction as indicated in FIG. I. The amount ofeccentricity determines the shape and size of the pumping chamber 54,which in turn determines the displacement on the pump itself.

A second sealing pin 55 is positioned loosely in a slot 58 formed in theperiphery of the ring 22. It is positioned approximately 90 fromextension 23. Sealing pin 55 cooperates with the extension 28 to definea pressure cavity 60. Sealing pin 34 cooperates with the extension 28 todefine a sealing cavity 62, the arcuate extent of which is approximatelytwice that of the chamber 60.

Line pressure passage 52 is in communication with branch passage 64,-which extends to the pressure chamber 60. A second branch passage 66communicates with the pressure chamber 62 on the upper side of the camring 22. This same passage 66 makes communication with the feed circuitfor the hydrokinetic torque converter which includes feed passage 68.

A pressure regulator valve element 70 is slidably positioned in valvechamber 72. Element 70 includes valve lands 74 and 76, the lattercontrolling distribution of pressure from line pressure passage 52 andlow pressure branch passage 66, the former controlling distribution ofpressure from line pressure passage 52 to exhaust port 78.

The upper end of land 74 is in fluid communication with the passage 52and is subjected to the pressure therein thereby normally tending tourge regulator valve element 70 in an outward direction. This pressureforce is opposed by pressure boost forces acting in the oppositedirection on the valve element 70.

The pressure forces induced on the ring 22 in a downward direction bythe pressure on the low pressure side of the regulator valve tends todecrease pump displacement. Pump line pressure, which acts on the lowerside of the cam ring, opposes the pressure force acting on the upperside of the cam ring. These forces balance each other and adjust thepump eccentricity to provide the required amount of pump flow. Thearcuate space between the sealing pins 55 and 34 communicates with thelow pressure port 44 through a cross-over passage 80.

The pump line pressure force is determined in the usual way, and itresponds to changes in the driven speed of the transmission mechanismand the torque requirements of the driveline. When the line pressuredrops below its scheduled value, the regulator valve element 70 moves inan upward direction thereby diverting flow from the converter circuitand reducing the pressure on the upper side of the ring. The forcesabove and below the ring thus become unbalanced and the ring movesupwardly thereby increasing the pump flow and restoring the scheduledvalue. The regulator valve element 70 then moves downwardly thusincreasing the pressure acting on the upper side of the ring and movingit down to reduce the pump flow.

Since the forces acting on the cam ring are balanced, the ratio of theforces that maintain that balance depends upon the location of thesealing pins. Additional pressures can be applied also to the ring ifthis is desired. For example, governor pressure may be used as a controlvariable in addition to the converter pressure. This would causeconverter pressure to be reduced upon an increase in the vehicle speed.

In FIG. 3, I have shown an alternate pivot arrangement between the camring and the pump housing. In this instance, the cam ring may beprovided with an eyelet extension 82. A pivot pin 84 is received throughthe eyelet extension 82 and is anchored in cooperating' openings formedin the adjacent housing. This arrangement requires, however, the use ofan additional seal pin 86 situated in seal recess 88. The location ofthe pin 86 is adjacent the pilot extension 82. The other elements of thepump of FIG. 3 have been identified by the same reference charactersused for corresponding elements of the FIG. 1 construction, althoughprime notations are added.

In FIG. 4, I have shown an alternate regulator valve circuit for use ina structure similar to that of FIG. 1. In the embodiment of FIG. 4, Ihave used reference characters that correspond to reference charactersused in identifying the elements of the circuit of FIG. 1, althoughdouble prime notations have been added. In the FIG. 4 embodiment, theregulator valve includes a modified valve element 90. This includesvalve lands 92, 94 and 96 which register with internal valve landsformed in valve chamber 98.

Upon an increase in the pressure boost forces in the embodiment of FIG.4, communication between line pressure passage 52 and the converter feedcircuit is decreased, as is the degree of communication between the linepressure passage 52 and the branch passage 66' extending to the top sideof the cam ring. This causes an increase in the displacement of the pumpwhich results, of course, in an increase in the line pressure. Theproper pressure balance then is restored to the value that correspondsto the pressure boost forces acting on the valve element 90.

Having thus described preferred embodiments of my invention, what Iclaim and desire to secure by U.S. Letters Patent is:

1. A positive displacement fluid pump comprising a pump body, a pump camring in said body, a pump rotor rotatably mounted in said cam ring,pumping elements carried by the periphery of said rotor and slidablyregistering with said cam ring, a pumping chamber defined by said rotorand said cam ring, inlet and outlet fluid ports communicating with saidpumping chamber, a pivotal connection between said cam ring and saidbody, said connection accommodating movement of said cam ring withinsaid body with respect to said rotor whereby eccentricity of said rotorwith respect to said cam ring may be varied, a transverse opening in theouter periphery of said cam ring, at least one sealing pin situatedbetween said housing and the cam ring and located in said transverseopening with a loose fit, said cam ring and said housing cooperating todefine a pair of pressure chambers therebetween, said sealing pinisolating one pressure chamber with respect to the other, a first fluidconnection between said outlet port and one fluid chamber, a secondfluid connection between the other pressure chamber and a low pressureregion of said system, and pressure regulator valve means in fluidcommunication with said fluid connections whereby pressure forces actingon said cam ring may be changed thus effecting variations in the fluiddisplacement of said pump.

2. The combination as set forth in claim 1 wherein said regulator valvemeans comprises a movable valve element having a pressure area thereonin fluid communication with said outlet port whereby a valve actuatingforce on said valve element is established, said pressure force tendingto urge said valve element in a direction that increases the degree ofcommunication between said fluid connections thereby varying thepressure force balance acting on said cam ring to decrease thedisplacement of said pump.

3. The combination set forth in claim 2 wherein said pump cam ringincludes further a second transverse opening in said cam ring and asecond sealing pin therein which is angularly spaced with respect tosaid one sealing pin and situated between the cam ring and said housingwhereby the arcuate extent of said one pressure chamber is less than thearcuate extent of said other pressure chamber.

4. The combination set forth in claim 2 wherein the pivotal connectionbetween said cam ring and said housing comprises innerconnected pivotelements one of which is formed on said housing and the other of whichis formed on said cam ring, the pivot axis for said pivotal connectionbeing parallel to the geometric axis of said rotor whereby the center ofsaid cam ring and the center of said rotor substantially correspond toeach other at a point midway between the two extreme positrons.

5. The combination set forth in claim 1 wherein the pivotal connectionbetween said cam ring and said housing comprises innerconnected pivotelements one of which is formed on said housing and the other of whichis formed on said cam ring, the pivot axis for said pivotal connectionbeing parallel to the geometric axis of said rotor whereby the center ofsaid cam ring and the center of said rotor substantially correspond toeach other at apoint midway between the two extreme positions of saidcam ring.

6. The combination set forth in claim 1 wherein said pump cam ringincludes further a second transverse opening in said cam ring and asecond sealing pin therein which is angularly spaced with respect tosaid one sealing pin and situated between the cam ring and said housingwhereby the arcuate extent of said one pressure chamber is less than thearcuate extent of said other pressure chamber.

7. The combination set forth in claim 6 wherein the pivotal connectionbetween said cam ring and said housing comprises innerconnected pivotelements one of which is formed on said housing and the other of whichis formed on said cam ring, the pivot axis for said pivotal connectionbeing parallel to the geometric axis of said rotor whereby the center ofsaid cam ring and the center of said rotor substantially correspond toeach other at a point midway between the two extreme positions of saidcam ring.

8. The combination set forth in claim 3 wherein the pivotal connectionbetween said cam ring and said housing comprises innerconnected pivotelements one of which is formed on said housing and the other of whichis formed on said cam ring, the pivot axis for said pivotal connectionbeing parallel to the geometric axis of said rotor whereby the center ofsaid cam ring and the center of said rotor substantially correspond toeach other at a point midway' between the two extreme positions of saidcam ring.

1. A positive displacement fluid pump comprising a pump body, a pump camring in said body, a pump rotor rotatably mounted in said cam ring,pumping elements carried by the periphery of said rotor and slidablyregistering with said cam ring, a pumping chamber defined by said rotorand said cam ring, inlet and outlet fluid ports communicating with saidpumping chamber, a pivotal connection between said cam ring and saidbody, said connection accommodating movement of said cam ring withinsaid body with respect to said rotor whereby eccentricity of said rotorwith respect to said cam ring may be varied, a transverse opening in theouter periphery of said cam ring, at least one sealing pin situatedbetween said housing and the cam ring and located in said transverseopening with a loose fit, said cam ring and said housing cooperating todefine a pair of pressure chambers therebetween, said sealing pinisolating one pressure chamber with respect to the other, a first fluidconnection between said outlet port and one fluid chamber, a secondfluid connection between the other pressure chamber and a low pressureregion of said system, and pressure regulator valve means in fluidcommunication with said fluid connections whereby pressure forces actingon said cam ring may be changed thus effecting variations in the fluiddisplacement of said pump.
 2. The combination as set forth in claim 1wherein said regulator valve means comprises a movable valve elementhaving a pressurE area thereon in fluid communication with said outletport whereby a valve actuating force on said valve element isestablished, said pressure force tending to urge said valve element in adirection that increases the degree of communication between said fluidconnections thereby varying the pressure force balance acting on saidcam ring to decrease the displacement of said pump.
 3. The combinationset forth in claim 2 wherein said pump cam ring includes further asecond transverse opening in said cam ring and a second sealing pintherein which is angularly spaced with respect to said one sealing pinand situated between the cam ring and said housing whereby the arcuateextent of said one pressure chamber is less than the arcuate extent ofsaid other pressure chamber.
 4. The combination set forth in claim 2wherein the pivotal connection between said cam ring and said housingcomprises innerconnected pivot elements one of which is formed on saidhousing and the other of which is formed on said cam ring, the pivotaxis for said pivotal connection being parallel to the geometric axis ofsaid rotor whereby the center of said cam ring and the center of saidrotor substantially correspond to each other at a point midway betweenthe two extreme positions.
 5. The combination set forth in claim 1wherein the pivotal connection between said cam ring and said housingcomprises innerconnected pivot elements one of which is formed on saidhousing and the other of which is formed on said cam ring, the pivotaxis for said pivotal connection being parallel to the geometric axis ofsaid rotor whereby the center of said cam ring and the center of saidrotor substantially correspond to each other at a point midway betweenthe two extreme positions of said cam ring.
 6. The combination set forthin claim 1 wherein said pump cam ring includes further a secondtransverse opening in said cam ring and a second sealing pin thereinwhich is angularly spaced with respect to said one sealing pin andsituated between the cam ring and said housing whereby the arcuateextent of said one pressure chamber is less than the arcuate extent ofsaid other pressure chamber.
 7. The combination set forth in claim 6wherein the pivotal connection between said cam ring and said housingcomprises innerconnected pivot elements one of which is formed on saidhousing and the other of which is formed on said cam ring, the pivotaxis for said pivotal connection being parallel to the geometric axis ofsaid rotor whereby the center of said cam ring and the center of saidrotor substantially correspond to each other at a point midway betweenthe two extreme positions of said cam ring.
 8. The combination set forthin claim 3 wherein the pivotal connection between said cam ring and saidhousing comprises innerconnected pivot elements one of which is formedon said housing and the other of which is formed on said cam ring, thepivot axis for said pivotal connection being parallel to the geometricaxis of said rotor whereby the center of said cam ring and the center ofsaid rotor substantially correspond to each other at a point midwaybetween the two extreme positions of said cam ring.